Trained in stage and costume design at the Swinburne Technical College, she directed a short, The Roof Needs Mowing, as part of a film class requirement. She then moved to Sydney, where she enrolled in 1973 in the Film and TV School, eking out a living as a waitress. On the strength of three shorts—100 a Day, Satdee Night, and Gretel—she entered the film industry as an assistant director. She won a top award at the 1976 Sydney Film Festival for the hour-long featurette The Singer and the Dancer and international accolades for her first full-length feature, My Brilliant Career. The film about an independent young woman with literary aspirations in turn-of-the-century Australia won the British Critics' Award for best first feature and seven AFI Awards, including best film and best director; it also brought lead actress Judy Davis to worldwide attention. Armstrong has made some films in America, beginning with Mrs. Soffel, but these have not been as well received as her Australian work.